Figure 1

The tendon repair and regeneration toolbox. Advancements in cell biology have made available a number of stem cell populations for tendon repair. Injectable carriers can act as stem cell carriers with potential to enhance clinical outcomes, especially in small defects. This strategy also offers the benefit of being minimally invasive, which is of critical importance, particularly for repeated or staged cell transplantations. Tissue grafts and anisotropic scaffolds are favoured for large tendon injuries. Such systems mimic the biophysical milieu of native tendons, offer an excellent three-dimensional environment for cell infiltration and growth, and facilitate directional cell growth and new tissue formation in vivo. Although cell-sheets have not taken off for tendon repair, preliminary results are very promising indeed and we anticipate their efficacy to be investigated further in the future, either alone or in combination with a carrier system that would provide adequate mechanical properties, whilst preserving cell phenotype for the period required to develop the implantable device. The therapeutic potential of the carrier systems can be further enhanced using bioactive/therapeutic molecules; controlled release capabilities amplify the in vivo potency of the implanted cells, whilst positively interacting with the host. ADSC, adipose-derived stem cell; BMSC, bone marrow-derived mesenchymal stem cell; iPSC, induced pluripotent stem cell; SC, stem cell; TSC, tendon stem cell.